The prefrontal cortex (PFC) in humans is associated with executive function. Patients with lesions to the PFC have deficits in executive function including planning, response inhibition, working memory, behavioral flexibility, and attention. Medical interest has focused extensively on the PFC because executive dysfunction is also present in nearly every neurological and psychiatric disorder including schizophrenia, obsessive compulsive disorder, attention-deficit/hyperactivity disorder, and Alzheimer's disease as well as aging. Thus, an understanding of the function of the PFC would help illuminate brain function in both the normal and diseased state. This proposal focuses on the role of the PFC in behavioral flexibility using the rat as a model organism. We hypothesize that behavioral flexibility is composed of two separate processes - strategy switching andreversal ~ andthat these processes can be assigned to two separate regions in the rat's brain -- the prelimbic/infralimbic (PL-IL) and the orbitofrontal cortex (OFC). A double dissociation experiment using selective inactivation of each region is proposed. Also, the neuronal encoding in each region will be investigated using high-density electrical recording. Brief description: All animals must flexibly adapt to changes in their environment in order to survive, yet in some human diseases the ability of people to adapt is impaired. This proposal attempts to define the regions in the brain that are involved in flexible behavior in rats. It also attempts to determine what types of information those brain areas encode by performing electrical recordings in the brains of behaving animals.